Calculate the following from the given diagram (in attachment)
1) Change in PE
2) Work done by F
3) Work done by Friction
4) Force of Friction
(Value of g = 10 m/s²)
(F = 20N)
Answers
Explanation:
Calculating the Amount of Work Done by Forces
Definition and Mathematics of Work
Calculating the Amount of Work Done by Forces
Potential Energy
Kinetic Energy
Mechanical Energy
Power
In a previous part of Lesson 1, work was described as taking place when a force acts upon an object to cause a displacement. When a force acts to cause an object to be displaced, three quantities must be known in order to calculate the work. Those three quantities are force, displacement and the angle between the force and the displacement. The work is subsequently calculated as force•displacement•cosine(theta) where theta is the angle between the force and the displacement vectors. In this part of Lesson 1, the concepts and mathematics of work will be applied in order to analyze a variety of physical situations.
Check Your Understanding
Express your understanding of the concept and mathematics of work by answering the following questions. When done, click the button to view the answers.
1. Apply the work equation to determine the amount of work done by the applied force in each of the three situations described below.
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2. On many occasions, there is more than one force acting upon an object. A free-body diagram is a diagram that depicts the type and the direction of all the forces acting upon an object. The following descriptions and their accompanying free-body diagrams show the forces acting upon an object. For each case, indicate which force(s) are doing work upon the object. Then calculate the work done by these forces.
Free-Body
Diagram
Forces Doing Work
on the Object
Amount of Work Done
by Each Force
A 10-N force is applied to push a block across a friction free surface for a displacement of 5.0 m to the right.
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A 10-N frictional force slows a moving block to a stop after a displacement of 5.0 m to the right.
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A 10-N force is applied to push a block across a frictional surface at constant speed for a displacement of 5.0 m to the right.
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An approximately 2-kg object is sliding at constant speed across a friction free surface for a displacement of 5 m to the right.
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An approximately 2-kg object is pulled upward at constant speed by a 20-N force for a vertical displacement of 5 m.
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